Drillstring structure

ABSTRACT

Two way flow tube system for deep water circulating mud drillstrings. The two-way flow tube system is arranged between the power swivel and the drilling bit. It has an upper end of one of the flow ways hydraulically communicating with a circulating mud inlet. The lower end thereof is hydraulically connected with the circulating mud outlet at the drillstring bit. The upper extremity of the other of the flow ways is hydraulically connected with the circulating mud outlet. The lower extremity thereof opens into the surrounding environment. Thereby the mud present in the surrounding environment may flow into the other flow way.

United States Patent 1191 Brunato May 6, 1975 DRILLSTRING STRUCTURE745,916 5/1944 285/137 R [76] inventor: Siro Brunato, Via G. Galli 23,

Melegnano Italy 2007 Primary Examiner-Thomas F. Callaghan [22] Filed:June 26, 1972 Attorney, Agent, or FirmDr, Guido Modiano; Dr. 211 App].N11; 266,085

[52] U.S. 285/137 A; 138/115; 285/334 51 1111. C1 F16] 39/00 ABSTRACT[58] Field of Search 285/137 R, 137 A, 333,

285/334, 355, 390; 138/116, H7, 115, 155 Two way flow tube system fordeep water circulating mud drillstrings. The two-way flow tube system isar- [56] References Cited ranged between the power swivel and thedrilling bit.

UNITED STATES PATENTS It has an upper end of one of the flow wayshydraulically communicating with a circulating mud inlet. The $33231Z1332 3332?.5:5::JJJJJJJJJJJJJJJJJJJ: iii/5Z5 low end llleleol lshydraulically comlwed wllll llle 1355:2396 10 1920 Decker 138/1 16circulating mud Oullel at the drlllslring The "PP 1,876,627 9/1932 Daviset al. 285/333 x extremity of the other of the flow y is hydraulicallyl,953,70l 4/1934 Clark et al.... 138/! I5 X connected with thecirculating mud outlet. The lower ,627 3/1938 Hinde iter-.. 285/333 Xextremity thereof opens into the surrounding environ- 3 9 8/1967 Price285/l37 R merit. Thereby the mud present in the surrounding en-3,489,438 l/l970 McClure 285/334 X vironmem may flow into the other nway.

FOREIGN PATENTS OR APPLICATIONS 773,67l 9/l934 France 285/137 R 1 Claim,7 Drawing Figures PATENTEDMAY' 6:975

SHEEI 10F 2 121 3 PR/ORART PMENIEBHAY' ems SHEET 2 BF 2 DRILLSTRINGSTRUCTURE BACKGROUND OF THE INVENTION The present invention relates todrillstrings and drillpipes thereof particularly for use in offshoredrilling.

As known at present in the art for drilling offshore wells on the seabeduse is made of a vessel or floating unit which is held on the verticalaxis of the well to be drilled both with static mooring systems andselfadjusting propulsors.

One of the main elements common to the known technologies is the riser"tube which has a diameter of either 16 or 24 inches fixed by means of aflexible seal joint to a safety equipment located at the wellhead on theseabed. This riser tube from the safety equipment extends upwardly to adetermined level above the water level and is kept constantly in atensioned condition through a pneumatic jack system arranged on theunit.

The riser has two important functions, i.e., the return of the drillingmud to the surface and guiding of tools into the well.

On the other hand it is due to the structure of this riser tube atpresent in use that serious limitations arise in drilling offshore wellsto a substantial depth. In fact, the weight of the riser, its diameter,fatigue stress and tensioning limitations are the most limitingparameters.

SUMMARY OF THE INVENTION The main object of the invention is that ofsubstantially eliminating the above mentioned limitation in drillingoffshore wells to a larger water depth then that attained heretofore.

Still another object of the present invention is that of providing atube system having a simple structure al lowing to eliminate theconventional riser tube.

These and still further objects are attained by a twoway flow tubesystem arranged between the power swivel and the drilling bit of a deepwater circulating mud drillstring, the two-way flow tube system havingan upper end of one of the flow ways hydraulically communicating with acirculating mud inlet, the lower end thereof being hydraulicallyconnected with the circulating mud outlet at the drillstring bit, andhaving the upper extremity of the other of the flow ways hydraulicallyconnected with the circulating mud outlet, the lower extremity thereofopening into the surrounding environment thereby allowing the mudpresent in the surrounding environment to flow into said other flow way.

BRIEF DESCRIPTION OF THE DRAWING An embodiment of the invention isillustrated in the accompanying drawings in which:

FIG. 1 shows diagrammatically a conventional drillstring;

FIG. 2 shows diagrammatically a drillstring including the two-way flowtube system according to this invention;

FIG. 3 shows a lateral view, partly in section, of the twoway flow tube;

FIG. 4 is an enlarged representation, partly in longitudinal section ofa joint of two two-way flow tubes;

FIG. 5 is a top view of FIG. 3, shown in an enlarged scale;

FIG. 6 is a cross-section according to VlVl of FIG. 3;

FIG. 7 is a view from below of FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENTS The conventional drillstring shownin FIG. 1 comprises a kelly joint 1, conventional drillpipes 2,drillcollars 3 and a bit 4. This drillstring is capable of carrying outthe normal sequence of known drilling operations. The equipment includesfurther a safety equipment 5 of known type, i.e., of the typemanufactured by Cameron Iron Works Houston Shaffer Tool Works BeaumontThis safety equipment is installed at the wellhead on the seabed 8. Twohoses are attached to this equipment, one of the hoses is a chokeline 6and the other a kill-line 7, which are employed during particularemergencies to re-establish the hydrostatic control of the well 10.

The conventional offshore drilling equipment comprises always a risertube 8, which has a diameter preferably of either 16 or 24 inches andwhich carries out two important functions:

return of the drilling mud to the surface,

guiding of tools into the well.

The riser 8 is suspended by means ofa series of pneumatic jacks (notshown) installed in a known manner on the floating unit. Owing to thecomplications involved, the riser represents, given the actual offshoredrilling technologies (ambient conditions and design characteristics)the most restrictive piece of equipment as far as the operating waterdepth is concerned.

The elimination of the riser in the offshore drilling equipment shouldtherefore be considered a great technological achievement in offshoredrilling technologies.

FIG. 2 illustrates the offshore equipment in which use is made of theapplicant's structure.

In order to nullify the vertical oscillation otherwise transmitted tothe drillstring by the floating unit due to wave action, use isadvantageously made of a conventional Motion Compensator, for instanceof the type manufactured by Vecto Offshore Industries, Inc VenturaCalifornia Shaffer Tool Works Beaumont The rotation is transmitted tothe drillstring by means of an electric power swivel also ofconventional type, such as the one manufactured by Bowen Tools, Inc.Houston The power swivel allows the circulation of the mud and for thepurpose it is connected with a mud inlet pipe 13 through which the mudenters the drillstring and the mud outlet pipe 14 through which the mudflows out from the drilling string.

The two-way flow drill pipe system I5 of the drillstring extends fromthe power swivel 12 down to beyond the safety equipment 5 and constitutethe socalled top section of the drilling string. This section isvariable in length according to drilling progress underneath the safetyequipment.

The lower end of the two-way flow drill pipe system of this invention isconnected to the conventional drillpipes 2 and near the connection pointlateral apertures 15a are provided in the peripheral wall defining thatflow way which is destined to allow the circulation of the mud from thewell towards the outlet end 14. Conventional drill collars 3 and aconventional bit 4 complete the drillstring. A rotating head preventer16', for instance of the type manufactured by Hydril Company Los Angelesprotects against loss of circulating mud and provides the hydraulic sealagainst the drillpipes of the invention. It may operate in a mannersimilar to a slufiing box.

Advantageously guidelines 17' are provided for han dling the equipment.

During drilling operations, the circulating mud is pumped through theswivel l2 and descends into the well passing first through one of thetwo flow ways of the drillpipes l5 and then through the conventionaldrillpipes 2 and finally exits through the bit 4, rising to the surfacealong the well annular space and, at the top of the section, through thesecond flow way of the drillpipes 15.

From the foregoing it will be understood that the offshore equipmentincluding the structure of this invention allows the elimination of theriser tube, makes it possible to operate in considerable depths ofwater, eliminates the chokeand kill-lines, simplifies the subseaequipment, and allows better operating conditions.

It is further important to note that the operating safety has beenincreased with the equipment of this in vention, inasmuch as thedrilling mud circulates in a closed circuit and at an adjustablepressure, allowing for a continuous well control and rapid interventionin case of gas manifestation.

FIGS. 3 to 7 illustrate the structure of the two-way flow pipe of thisinvention. The partition wall divides the interior of the pipe in twoflow ways 16 and 17, respectively. At both ends of the pipe, pipe headsl8 and I9 are provided. the pipe head 18 having an inner female screwthread 21 and the pipe head 19 having an outer male screw thread 22.these male and female screw threads of corresponding adjoining pipesbeing adapted to mutually mate as shown in FIG. 4.

At the ends of both pipeheads l8 and 19, abutment surfaces 23 and 24 areprovided, respectively. The abutment surface 23 is provided with acircular recess for receiving a gasket 25. Also the abutment surface 26of the partition wall 20 has a recess for receiving a diametral portionof the gasket 25 as visible in FIG. 5. The partition 20 enlarges nearthe head 19 of the pipe to form an enlarged abutment surface 27 in orderto guarantee a seal effect over a certain angle. From FIG. 7 of thedrawing it clearly appears that the abutment surface 27 tapers from theperiphery towards the center of the tube. In this manner the union ofthe two joints is ensured as long as thread slippage remains within theabovementioned angle alpha.

The described pipe structure provides a simple and effective joint.

The known component parts of the described drillstring are disclosed inthe Composite Catalog of Oilfield Equipment and Services published byWorld Oil.

1 claim:

1. A two-way flow tube for a drillstring comprising a longitudinalpartition wall within the interior of the tube, extending over thelength of the tube and separating the tube into two longitudinal tubularcompartments, the tube having a female inner screwthread at one endthereof and a mating male screw thread at the other end thereof, saidpartition wall having abutment surfaces at both extremities thereof forsealing engagement with partition walls of corresponding two-way flowtubes, said partition wall extending according to a diametral plane andhaving at, at least one end thereof a seat for a sealing gasket, whereinthe tube ends have circular abutment surfaces, at least one of saidsurfaces having circular seats for sealing gasket means, and wherein thepartition wall has enlargements at, at least one end thereof thereby toincrease the abutment surfaces thereof, said enlargements tapering fromthe periphery towards the center of the tube at least at the abutmentsurfaces thereof.

l k i i

1. A two-way flow tube for a drillstring comprising a longitudinalpartition wall within the interior of the tube, extending over thelength of the tube and separating the tube into two longitudinal tubularcompartments, the tube having a female inner screwthread at one endthereof and a mating male screw thread at the other end thereof, saidpartition wall having abutment surfaces at both extremities thereof forsealing engagement with partition walls of corresponding two-way flowtubes, said partition wall extending according to a diametral plane andhaving at, at least one end thereof a seat for a sealing gasket, whereinthe tube ends have circular abutment surfaces, at least one of saidsurfaces having circular seats for sealing gasket means, and wherein thepartition wall has enlargements at, at least one end thereof thereby toincrease the abutment surfaces thereof, said enlargements tapering fromthe periphery towards the center of the tube at least at the abutmentsurfaces thereof.